A huge slab of sandstone discovered in Balfron parish, near Stirling, has been identified as a polissoir (a hard block used for polishing or sharpening hand-axes) that may have first been used during the early Neolithic period. Handheld examples have previously been found in Orkney, but this is the first large, bedrock polissoir to be identified in Scotland, and may be the only one recorded in the whole of north-western Europe.
The slab, which is situated along a ridge between two valleys, was first identified in the 1970s by a member of the public, but it received little academic attention until George Currie noted the presence of rock carvings in 2012. This led to a visit from Scotland’s Rock Art Project (ScRAP; see CA 344 and CA 377) researchers, who revealed its true significance. After stripping away some of the surrounding turf, ScRAP volunteers quickly identified not only cup marks – probably dating to the late Neolithic or Bronze Age – on its surface, but also noted many different cut marks from hand-axes, indicating its use as a polissoir during the early Neolithic. The discovery of several stone roughouts on the slab suggested that part of the site had been used for quern quarrying, possibly during the Iron Age or early medieval period. It appears that this site had been a significant place for local communities for millennia.
Since then, a large team drawn from across Scotland, including Murray Cook (Stirling Council’s Archaeologist), Nick Parish (ScRAP), researchers from National Museums Scotland, archaeology students, and other volunteers, have spent the better part of three years stripping the entire site (an area of roughly 200m by 25m) and recording it. A drone survey was also carried out by David Connolly, while photogrammetry was undertaken by AOC Archaeology and funded by Forestry and Land Scotland and Historic Environment Scotland. Fieldwork concluded this past November, when the site was backfilled, though analysis of the carvings is ongoing, undertaken by students Irene Dayer and Grace Heller.
Initial investigations of the markings have found that the hand-axe grooves do not form any discernible pattern, comprising many different depths and orientations. Were the different groove depths used for attaining different levels of sharpness, or had they been made by different types of axe or perhaps by different members of a family group? Unusually, no flint debitage from the hand-axes was discovered, although there was plenty of worked quartz scattered across the site, suggesting that it had potentially been used for marking and/or sharpening other stone tools as well.
While post-excavation analysis of the polissoir’s use and significance continues, the fact that – unlike those found in Orkney – this example is not portable could indicate that it might have been intended for ceremonial, rather than practical, purposes. It would have required Neolithic people to come specifically to this location, perhaps from some distance away, as there are no known settlements from this time nearby (although the Neolithic landscape of this area is not well documented).
Some unusual characteristics of the site lends further credence to this hypothesis. For instance, the edges of the slab, which is bright white, are marked with a series of unusual patterns, which were first mistaken for rock art. It has since been established that these markings are natural, probably from the acid of tree roots cutting into the rock. The team hypothesises that it may have been these enigmatic features that first led people to use this slab to grind axes. Interestingly, the site lies just short of the very top of the ridge, where the best views would have been (though today it is covered by a conifer plantation). Could this polissoir have been related to some sort of ceremonial location nearby? It is hoped that, as post-excavation work continues, more answers will come to light.